You only need to write a statement, which is roughly as follows:

I (or xx company, unified social credit code xxxxx) provided agricultural mechanization farming operations for xxx, and earned income of nnnn yuan, which belongs to tax-free filing income.

Hereby declare

xxx

(or xxx company seal)

Date, year and month

Of course, the payer (service recipient or service provider) had better write a statement:

Xxx (or xxx company) provides me with nnn mu of agricultural mechanization farming, and we need to pay nnn yuan.

Hereby certify that

xxx

Date, year and month