Services Invoice Approval Software: Approve SES-less Invoices With Proof

Services invoice approval software checks a services invoice against its purchase order and the proof the work was done. It then records who approved it, and in what order. For services, that proof is the service entry sheet (SES), and it is the document most often missing when the invoice arrives.

A Head of AP at a manufacturer running SAP sees it every month-end. Maintenance, security, IT support and consulting invoices land against valid POs, but nobody has confirmed the work. The invoice gets approved on the strength of the PDF alone.

That is an SES-less invoice. KlearStack checks each one against the PO, the service confirmation and your approval policy before it is paid, and logs the result for your auditor. This guide covers what an SES is, why it goes missing, and what approval should rest on.

TL;DR

1. A services invoice should be approved on proof of the work, not on the invoice PDF.
2. The service entry sheet (SES) is that proof in SAP; it does for services what a goods receipt does for materials.
3. SES-less invoices are common because the person who confirms the work rarely sits in AP or in SAP.
4. An approved invoice is not an approved service: the invoice approval signs off a claim, the SES signs off the work.
5. The Date-Order Test: PO, service period, SES acceptance, invoice, approval. If the SES is dated after the invoice, it was raised to clear the invoice.
6. In India, missing proof of receipt puts input tax credit at risk, and slow approvals push MSME payments past 45 days.
7. Approval software should check the evidence behind each signature, not only route the invoice.
8. Start with 50 recent services invoices and check the dates.

Run 50 of last month’s services invoices through KlearStack’s checks

What Is a Service Entry Sheet?

A service entry sheet is the buyer’s record that services ordered on a purchase order were performed and accepted. It lists the work, quantity or hours, period and value against the PO lines. In SAP it is created and accepted in transaction ML81N, and invoice verification in MIRO is then posted against it.

Materials have a goods receipt note: someone counts what arrived. Services have no box to count, so the service entry sheet carries the same weight. An Accounts Payable Manager treats it as the third leg of the match.

The match is the same logic as three-way matching in accounts payable, with the SES standing in for the GRN. The hard part is that the person who should create it is usually not in finance.

Why Services Invoices Arrive Without Service Entry Sheet

Services invoices arrive without an SES because the work is confirmed by someone outside AP who has no reason to log into SAP. The vendor invoices on its own calendar, the SES waits for a busy site manager, and the shared services lead waits for both.

• The confirming owner is a plant, facility or project manager who rarely uses SAP.
• The vendor bills monthly on a framework PO, but the work is accepted weekly or not at all.
• Milestone or partial services do not map neatly to PO lines, so nobody knows what to enter.
• The SES owner is on leave, has moved roles, or was never assigned on the PO.
• Month-end pressure turns the SES into a formality created after the invoice to let it post.

Industry-wide, a fifth of invoices already need human handling. Ardent Partners’ 2026 AP benchmarks put the average invoice exception rate at 19.9%, against 11.8% for the best teams. SES-less services invoices sit inside that number, and they are a different problem from the non-PO invoices that have no order at all.

What we see in AP teams that run SAP is that the SES gap is a calendar problem before it is a control problem. Vendors invoice on the 1st, site managers confirm work when they get to it, and AP closes on the 5th. Whoever owns the close ends up chasing signatures, and the chase is where the shortcuts start.

What Goes Wrong When SES-less Invoices Get Paid: The Rs 5 Lakh A to B to C Story

When an SES-less invoice is paid, the company pays for a claim nobody verified, and the approvers own that payment. KlearStack’s founder tells one version of this story to every AP head.

A company’s policy says any supplier invoice above Rs 5 lakh needs approval from A, then B, then C, in that order. The trail must be verifiable before the invoice falls due.

Take an illustrative Rs 6.2 lakh invoice for a month of plant maintenance. A, the site manager who should raise the SES, is on leave, so B approves from the PDF and C approves because B did.

The invoice is paid on time. At audit there is no SES, A never signed, and two of the four weeks of work were never done. Missed by hand, it is a business risk for the company and the signers, and somebody loses a job over it.

⚠️ Warning

An SES created after payment does not repair the control. It records that someone confirmed the work once the money had gone, and the date on it tells the auditor exactly that.

An Approved Invoice Is Not an Approved Service

The assumption is that once the invoice clears the approval workflow, the service has been approved. The reality is that invoice approval signs off a claim, while the SES signs off the work. A Financial Controller who approves the first without the second has approved a document, not a delivery.

The same gap is how invoice fraud gets through, which is why invoice fraud detection starts with what the invoice is checked against. Services are the easiest category to inflate, because there is nothing physical to count.

📊 65% of internal audit leaders name fabricated invoices or financial documents a leading AI-enabled fraud threat

The IIA’s February 2026 survey of 373 audit leaders also found 57% citing a lack of appropriate tools. A services invoice with no SES behind it gives a fabricated claim nothing to fail against.

Source: The IIA, February 2026

In India the cost reaches tax. Section 16(2)(b) of the CGST Act allows input tax credit only where the buyer has actually received the goods or services. An invoice with no record of receipt is a weak position in a GST audit.

What Should a Services Invoice Be Checked Against?

A services invoice should be checked against six things. They are the PO, the service confirmation, the contract rate, the vendor record, earlier invoices and the approval record. A Head of Procurement and a Head of AP can agree this list once and apply it to every services invoice.

1. The purchase order. Line, rate, validity period and remaining value, so a framework PO is not overrun.
2. The service confirmation. An accepted SES, or the completion certificate or timesheet your policy accepts, covering the billed period and quantity.
3. The contract or rate card. Hourly rates, fixed fees and escalation terms, not just the PO price.
4. The vendor record. Legal name, GSTIN and bank details as held in your vendor master.
5. Earlier invoices. The same invoice number, the same period or the same work billed twice, which our guide on tools to prevent duplicate invoices covers in detail.
6. The approval record. Who approved, in what order, and on which evidence.

The Date-Order Test: Five Minutes on 50 Invoices

A clean services invoice has five dates that fall in order: PO date, service period, SES acceptance, invoice date, payment approval. Pull 50 paid services invoices from last quarter and compare just two of them, the SES acceptance date and the invoice date.

Every invoice whose SES was accepted after the invoice arrived had its proof created to clear it. If more than a handful fail, your SES control is running backwards, and purchase order compliance on paper will not show it.

See which of your 50 latest services invoices fail the date-order test

What Software Can I Use to Automate Invoice Approval?

You can automate invoice approval with ERP workflow, standalone approval tools or AP automation software. For services invoices, the deciding question is whether the tool checks the evidence behind each approval or only moves the invoice along. A CFO comparing tools should test that on SES-less invoices first.

Most teams need the workflow and the check, not one or the other. Our guide to AI accounts payable software compares the wider category. For an invoice approval workflow, the test is whether a skipped approval shows before payment.

Approval Chains: Who Signs What, and on What Proof

An approval chain is only as good as the proof each signer sees. Your policy decides who signs and in what order. The control is that each signature rests on the SES, the PO and the contract, not the invoice alone.

KlearStack runs this through the AP Invoice Agent, inside Supply Chain Document Compliance. The agent matches the invoice to the PO and to the receipt document before posting to your ERP. For services, the receipt document is the SES or the confirmation your policy accepts.

• It lists the evidence missing from each invoice before the invoice moves.
• It compares rate, period and value across the invoice, PO and service confirmation, and names the field that differs.
• It flags an invoice, period or service already billed, and checks every document for tampering.
• It logs who approved and in what order, so a skipped or out-of-order approval shows before payment.

That record becomes the invoice audit trail a Head of AP can hand the auditor. KlearStack takes the drudgery; your team keeps the judgment and the final decision on every exception.

Before, an approver sees a PDF and a deadline, and the trail shows a signature. After, the approver sees the PDF with the PO, the SES and every mismatch beside it, and the trail shows what was checked. Clean invoices post at 95%+ STP within 90 days of go-live, and the agent sits beside your ERP, so nothing is replaced.

💡 Tip for AP and shared services teams

Agree with procurement which documents count as service confirmation when there is no SES: a signed completion certificate, an approved timesheet, or a site log. Written down once, it becomes a rule that can be checked on every invoice.

Related: Invoice matching automation

When This Is Not a Fit

If services spend is a handful of fixed monthly retainers, a calendar reminder and a second reviewer may be enough. If your service confirmations live only inside SAP screens and are never exported, confirm in the pilot how the agent will receive them. If the root cause is that nobody owns the SES, fix ownership on the PO first.

Conclusion

Services invoice approval works when every signature rests on proof of the work, not on the invoice PDF. The SES is that proof, and an SES dated after the invoice is a warning, not a fix. The test is simple enough to run this week on 50 invoices.

The cost of skipping it is real money. The ACFE’s Occupational Fraud 2026 report studied 2,402 cases with a median loss of about $104,000 each.

In India the delay costs too. Payments to micro and small suppliers made after 45 days are deductible only when paid. The rule now sits in section 37(2)(g) of the Income-tax Act, 2025, formerly section 43B(h).

A services invoice paid without an SES and approved out of order ends up in the audit report with three names on it. The job at risk is the one that signed off on the invoice nobody checked.

Book a demo on 50 recent services invoices

FAQs

What is ML81N in SAP?

ML81N is the SAP transaction used to create, change, display and accept service entry sheets against a service purchase order. The person who confirms the work records the services performed against the PO lines and accepts the entry sheet. Invoice verification for that PO can then be posted against the accepted sheet.

What is SES in billing?

In billing, SES stands for service entry sheet, the buyer’s record that billed services were performed and accepted. Many buyers that run SAP ask suppliers to quote the SES number on the invoice. Without it, the invoice usually waits in accounts payable until someone confirms the work.

How can I check a service entry sheet in SAP?

A service entry sheet can be displayed in transaction ML81N by its number, or found through the purchase order history in the PO display screen. The history lists entry sheets and invoices posted against each PO line. Checking whether the sheet is accepted, and its acceptance date, shows whether an invoice was confirmed before it was approved.

How do I create a service entry sheet in SAP?

In classic SAP MM, a user opens transaction ML81N, selects the service purchase order, enters the services performed against its lines, and saves the sheet. An authorised person then accepts it, which allows invoice verification against it. In SAP S/4HANA many companies use the Fiori app for service entry sheets instead.