Certificate of Residence forms for the year ahead

My company has a customer in Serbia, who requires a Certificate of Tax Residence in order to pay me net of local tax under the bilateral Double Taxation Agreement. They say that they require a certificate for the whole of the coming year, whereas I understand that HMRC only issues certificates for time past. How do I get around this impasse in the case of Serbia?

Hi,
If a Certificate of Tax Residence is required for a period partly or entirely in the future we cannot certify that a company will be residence in the UK for any accounting period which ends on a future date.  
However, we can issue a certificate of UK residence using the date that we sign it as the end date.  
Most of the countries that we are treaty partner with accept that certificates will be valid for up to 12 months.
Thankyou.