Invoicing, Proforma Invoices and VAT for Oilfield Suppliers

Where invoices actually fail

Payment delay in oilfield supply is rarely a dispute about the work. It is a missing purchase order reference, a TRN omitted, a service period that does not match the field ticket, or a rate that does not match the call-off schedule. Each of these sends the invoice back to the start of an approval cycle that can run a full month.

The fix is document discipline rather than escalation: raise the invoice against the order, quote every reference the client's system matches on, and attach the signed evidence of delivery in the same submission.

Tax invoice requirements to check before sending

For UAE-registered suppliers the FTA sets out what a tax invoice must carry. Confirm each item is present rather than assuming the template covers it.

• —The words "Tax Invoice", a unique sequential number and issue date
• —Supplier name, address and TRN; recipient name, address and TRN
• —Description, quantity and unit price per line, with the date of supply
• —Taxable amount, VAT rate, VAT amount and gross total per line
• —Reverse-charge or zero-rating statement where applicable, with reason
• —Purchase order, contract or call-off reference the client will match on

Proforma versus tax invoice

A proforma invoice is a commercial offer document, not a tax document. It exists so a buyer can open a letter of credit, release an advance or obtain internal budget approval before goods ship. It carries Incoterms, validity, packing and estimated freight, and it does not create a VAT liability. Issue a proforma invoice for advance payment with DocMak at that stage, then raise a compliant tax invoice with the DocMak Invoice Maker once supply occurs.

The chain around them matters as much: send a priced quotation with the DocMak Quotation Maker at enquiry stage, issue a purchase order to suppliers using DocMak when procuring inbound, produce delivery notes and payment receipts on DocMak at dispatch and settlement, and correct a billing error with the DocMak Credit Note Maker rather than by email adjustment.

Pricing the line before it is invoiced

Margin is lost at quotation, not at invoicing. On imported chemicals and equipment the delivered cost has to include freight, duty and clearance before a rate is offered, which is where the Tradloc logistics tools belong: calculate import duty and total landed cost on Tradloc, then check the tax treatment with the DocMak UAE VAT Calculator before the quotation is released. The shipping cost guide covers that calculation in full.