nets = [12000,24000,36000,48000,60000]

tax = {
    'personalAllowance' :    11850,
    'basicRate' :            0.2,
    'basicRateUpperLimit' :  46350,
    'higherRate' :           0.4,
    'higherRateUpperLimit' : 150000,
    'additionalRate' :       0.45
}
nic = {
    'lowerProfitsLimit' : 8424,
    'upperProfitsLimit' : 46356,
    'basicRate' :         0.12,
    'higherRate' :        0.02
}

threshold1 = nic['lowerProfitsLimit']
threshold2 = tax['personalAllowance'] - nic['basicRate'] * (tax['personalAllowance'] - nic['lowerProfitsLimit'])
threshold3 = (tax['personalAllowance'] + tax['basicRateUpperLimit']) - tax['basicRate'] * tax['basicRateUpperLimit'] - nic['basicRate'] * (nic['upperProfitsLimit'] - nic['lowerProfitsLimit'])
threshold4 = (tax['personalAllowance'] + tax['higherRateUpperLimit']) - tax['higherRate'] * (tax['higherRateUpperLimit'] - tax['basicRateUpperLimit']) - tax['basicRate'] * tax['basicRateUpperLimit'] - nic['higherRate'] * (tax['personalAllowance'] + tax['higherRateUpperLimit'] - nic['upperProfitsLimit']) - nic['basicRate'] * (nic['upperProfitsLimit'] - nic['lowerProfitsLimit'])

for net in nets:
    print "net: {}".format(net)

    if net <= threshold1:
        print net

    elif net <= threshold2:
        gross = (net - nic['basicRate'] * nic['lowerProfitsLimit']) / (1 - nic['basicRate'])

    elif net <= threshold3:
        gross = (net - (nic['basicRate'] * nic['lowerProfitsLimit']) - tax['basicRate'] * (tax['personalAllowance'])) / (1 - nic['basicRate'] - tax['basicRate'])

    elif net <= threshold4:
        gross = (net * 1 + nic['basicRate'] * (nic['upperProfitsLimit'] - nic['lowerProfitsLimit']) + tax['basicRate'] * tax['basicRateUpperLimit'] - nic['higherRate'] * nic['upperProfitsLimit'] - tax['higherRate'] * (tax['personalAllowance'] + tax['basicRateUpperLimit'])) / (1 - nic['higherRate'] - tax['higherRate'])

    else:
        gross = (net * 1 + nic['basicRate'] * (nic['upperProfitsLimit'] - nic['lowerProfitsLimit']) + tax['basicRate'] * tax['basicRateUpperLimit'] + tax['higherRate'] * (tax['higherRateUpperLimit'] - tax['basicRateUpperLimit']) - nic['higherRate'] * nic['upperProfitsLimit'] - tax['additionalRate'] * (tax['higherRateUpperLimit'] + tax['personalAllowance'])) / (1 - nic['higherRate'] - tax['additionalRate'])

    print "gross: {}".format(gross)
    print "----------"